Variable density article and method of making



Jan. 20, 1959 c KEMPER 2,869,947

VARIABLE DENSITY ARTICLE AND METHOD OF MAKING .Filed March 21, 1955 IN V EN TOR.

Byi p w W United States Patent 'Ofiice Patented Jan. 2%, E5955) VARIABLE DENSITY ARTICLE AND Mnrnoo or MAKING Charles R, lgemper, Dayton, Ohio Application March 21, 1955, Serial No. 495,678 6 Ciaims. (Cl. 309- 44) This invention relates to powdered metallurgy and particularly to a new article of manufacture and method of making such article characterized by a principleof varying density.

Some machine parts, such as piston rings and sealing rings, can advantageously use the'porosity' and'l'ackbf abrasive qualities of powdered metal but it has hefetof fore been felt that such parts did not lend 'themseliies to powdered metal production since it was also important that the inner peripheral edge of a piston or sealing ring be relatively dense and hard to permit of accurate machiriing and in. order thata spring temper may 'be. d e.-

or minimizes scratching and marring of the cylinder W 4 he. hi he si p t on. p rt u a y w th P e s: a r zv i n a be au d a e on he p r e Qt ta l and. n. a arvn. to a sp t mp if required.

The object of the invention is to simplify the construction as well as the means and method of making powtiered metal; articles, whereby such articles. may not only be. economically manufactured, but will be more efiicient and satisfactory in use, adaptable to a wide variety of applications, and be unlikely t 561 out of repair.

A further object of the invention is to produce a new article of' manufacture characterized as. above. described.

Another object of the invention is to present a method of rnalring a powdered metal article as above. described.

A further object of the invention'isto provide. for

mallcing of varying density powdered metal artic es. accgrding to an inventive concept involving only slight changes in the apparatus and methods commonly used in the manufacture of conventional powdered metal products. A further object of the invention is to provide a powdered metal article possessing the advantageous structurai features, the inherent meritorious characteristics and the mode of operation herein mentioned.

With the above primary and other incidental objects in view as will more fully appear in the specification, the invention intended to be protected by Letters Patent consists of the features of construction, the parts and combinations thereof, and the mode of operation as hereinafter described or illustrated in the accompanying drawings, or their equivalents.

Referring to the accompanying drawing wherein is shown one but obviously not necessarily the only form of embodiment of the invention,

Fig. 1 is a fragmentary view in cross section of a mold for performing one step of the. method of the instant invention;

" Fig' 2 is a view in cross section of an unfinished part as produced by the mold of Fig. 1;

EigJSf is a view like Fig. 1 showing the same or another mold adapted for the carrying out of a finishing step on the part of Fig. 2; and Fig. 4 is a view like Fig. 2, showing a finished part as produced by the mold ofFig. 3.

' L i epa'rts are indicated by similar characters of reference'throughout the several views.

Referring to the drawing, the practice of the method of the invention involves the use of generally conventional'tools and contemplates a two step operation. In the such step, a tool constructed in accordance with the showing of Fig. 1 may advantageously be used, such toolincluding a table or die plate 10, having a central tb rough pening 11 and concentric counter bores 12 and 13; A dil 14 is seated in the counter bore 12 and is held therein by a ring 15 seated in the counter bore 13 and having a flange 16 overlying an annulus 17- on the die 14. The latter has a central through opening. 18.

Aligned with the opening 18 and extending upward from beneath the table 10 is a core rod 19. A head 21 on the rod 19 extends into the opening 18 and is spaced from the wall of su ch opening in a manner to define an annular chamber or cavity 22. The bottom of such chamber. or cavity normally is closed: by a lower punch element 23 having a cylindrical portion 24 entering the lower end of the cavity 22. In opposing relation to the pungh 23 an upper punch 25, having a cylindrical portion 26 extending into. the upper end of the cavity 22 in opposing. relation to the cylindrical portion 214 of the lower punch2i3. The opposing adjacent ends of the punch elements 23 and 25 have respective, relatively inverted frusto-conical surfaces 27 and 28.

The upper punch 25 is arranged to be retracted a distance sufficient to withdraw the cylindrical portion 26 from the cavity 22 in, order that such, cavity may be filled or partly filled with granules of a selected metal. The upper punch 25 then is returned so that the cylindrical portion 26 may reenter the cavity 22. Under heavy applied impact or like pressure, the face 28- thereof engages the powdered metal, the lower punch 19 through its face 27 opposing longitudinal displacement of the powder with a reactant force of equal magnitude. Under the application of such pressures the granules of metal are in effect fused into a homogeneous mass, shaped in conformance with the shape. of the cavity 22 as defined by the faces. 27 and 28, the side wall of opening 18 and the surface of head 21 of the core rod 19. The article so formed is removed from the cavity 22 by withdrawal of one or both. of the punches 23 and 25 and becomes an unfinished part 29, shown in Fig. 2.

As indicated, the part 29 has a maximum thickness at the inner periphery thereof and tapers to a portion of thickness at the outer periphery. The ring may thus be said to have greater mass at its; inner periphery than at its outer periphery. It has, moreover, a substantially constant density since in its loose state the metal particles or granules may flow to all parts of the cavity 22 under the application of pressure so that final forming pressures applied by the opposing punch members result in an equal compacting of the metal of the ring over the entire body or volume thereof.

In the second step of operation, the unfinished part 29 is placed in a tool as shown in Fig. 3 which is constructed in a manner the same as the tool of Fig. 1 except for the cooperating faces of the punch elements. Thus, the tool of Fig. 3 comprises a table 31, a die 32 supported therein and a ring 33 holding the die 32 in place. A central through opening 34 in the die 32 receives one end of a core rod 35 and opposing cylindrical ends of punch elements 36 and 37. The latter present respectively opposing faces 38 and 39 which define a cavity 41 and are similar to the faces 27 and'28 except that they are square or in parallel planes at right angles to the axes of the punch elements. The unfinished part 29 is placed in the cavity 41 and an opposing pressure applied thereto by the lower and upper punch elements 36 and 37. During a major part of the effective travel of the punch elements the faces 38 and 39 engage the relatively thick inner periphery of the part 29 and further compact the metal granules whereby to achieve in this area a greater density. As the relative approaching motion of the faces 38 and 39 continues the entire ring is brought under compression in a manner to obviate displacement of material in the area of the outer periphery and to force the ring into a common plane, with the resultant or finished part being as shown at 42 in Fig. 4. By reason of the inclined formation of the body of the unfinished part 29, it will be understood that the increase in density as between the unfinished part 29 and the to the powdered metal through cylindrical punch elefinished part 42 is a graduated formation, increasing gradually from the outer periphery to the inner periphery. By change in the configuration of the tool faces 27 and 28 the transition from low to high density might be made more abrupt or more gradual as might be desired.

From the above description it will be apparent that there is thus provided a device of the character described possessing the particular features of advantage before enumerated as desirable, but which obviously is susceptible of modification in its form, proportions, detail construction and arrangement of parts without departing from the principle involved or sacrificing any of its advantages.

While in order to comply with the statute the invention has been described in language more or less specific as to structural features, it is to be understood that the invention is not limited to the specific features shown, but that the means and construction herein disclosed comprise but one of several modes of putting the invention into effect, and the invention is therefore claimed in any of its forms or modifications within the legitimate and valid scope of the appended claims.

Having thus described'my invention, I claim:

1. As a newarticle of manufacture, a varying density metal ring, said ring being made of powdered metal compacted to a controlled uniform minimum density at its one peripheral edge and uniformly increasing in density toward a maximum value at the other peripheral edge, said ring being formed in a homogeneous mass without separation lines between portions of different density.

2. As a new article of manufacture, a piston ring made of powdered metal, the outer peripheral portion of said ring being of uniform controlled density and the inner peripheral portion beingrelatively compacted and high in density, the area between said portions having a gradu- "meats provided with opposed relatively inverted frustoconical surfaces to provide a ring member having umform density and formed with frusto-conical projections at either face thereof, and applying cylindrical punch elements having opposed parallel surfaces to the opposite faces of said ring member to further compress the projecting portions thereof to provide an increased density of material to the ring in such portions thereof,

4. A method of making powdered metal rings of varying density including the steps of introducing powdered metal into an annular cavity, applying uniform pressure to the powdered metal through cylindrical punch elements provided with opposed relatively inverted uniformly graduated surfaces and forming a ring member having uniform density and formed with uniformly graduated projections at either face thereof, and applying generally cylindrical punch elements having opposed parallel flat surfaces to the opposite faces of said ring member to further compact the projections thereof and provide an increased density of material to the ring in such further compacted portions.

5. A piston ring or like article made of powdered metal in a plurality of steps, in a first of which an initial ring a a formation is achieved wherein the cross sectional area has a substantially uniform density and wherein the height of the ring tapers evenly from a maximum at one peripheral edge to a minimum at the other peripheral edge, and in a second of which the initial formation is changed by ated density uniting said peripheral portions without lines a of separation therebetween.

3. A method of making powdered metal rings of varying density including the steps of introducing powdered metal into an annular cavity, applying uniform pressure compacting the ring to a uniform height approximately equal to said minimum height, the density of the ring after said second step being at a maximum at said one peripheral edge and a decreasing gradually therefrom to a minimum at said other peripheral edge.

6. In powdered metallurgy, a method of making a powdered ring having an annular portion of relatively greater density than the remainder thereof, including the steps of applying a compressive force to powdered metal to form a ring of compacted powdered metal through use of a die means displacing some of the powder into a specific annular area of the ring to effect an integrated unfinished part of substantially constant density having an annular area of greater mass than the remainder thereof, 7

said die means presenting opposing frusto-conical shapes producing an unfinished part of maximum and minimum thicknesses at its respective peripheral edges, the upper and lower surfaces of the ring tapering between said edges, and subjecting said unfinished part to a further compressive force utilizing die means compacting said annular area of the unfinished ring into a common mass with the remainder of the ring to increase the density of I said further compacted area.

References Cited in the file of this patent UNITED STATES PATENTS Rice Feb. 6, 1951 

